Any art object—paintings, sculpture, jewelry, ceramics, fine furniture, and decorative pieces of all kinds—can be forged. The difficulty of forging, however, is as important as market price in determining what is forged. Probably fewer than 1 percent of stone sculptures are false because they require so much labour to make and their market is limited, but as many as 10 percent of modern French paintings on the market may be forgeries. The technical difficulties in making a convincing imitation of an ancient Greek vase are so great that forgeries are almost nonexistent. In contrast the forgery level of tiny archaic Greek and Cretan bronze statuettes, which are simple to cast, is possibly as high as 50 percent. A forger is most likely to succeed with a mediocre piece in the middle price range because such a piece probably will never be subjected to definitive examination. Although the price should be low enough to allay suspicion, the object can still yield a fair return for the effort expended by the forger.

The copy is the easiest forgery to make and is usually the easiest to detect. When a duplicate has appeared the problem is merely to determine which is the original and which is the copy. At least a dozen excellent replicas of Leonardo da Vinci’s Mona Lisa exist, many of them by his students. Various owners of these copies have at various times claimed that they possess the original. The Louvre is satisfied that it owns the painting by Leonardo because close examination reveals slight changes in the composition underneath the outermost layer of paint, and because this painting has an unbroken record of ownership from the time that the artist painted it.

A monumental sculptural forgery was a copy based on a Greek bronze statuette of a warrior of 470 BC, only five inches high and located in the Antikenabteilung, Berlin. The forgers made an eight-foot-high reproduction of it in terra-cotta and offered it as an Etruscan masterpiece. The resemblance was noted by the experts, who thought it to be an example of an Etruscan artist borrowing a Greek design motif. In 1961, after it had been in the Metropolitan Museum of Art in New York for 40 years, an analysis was made of the black glaze that covered the figure. It was found that the glaze contained as a colouring agent manganese, which never was used for this purpose in ancient times. Finally, Alfredo Adolfo Fioravanti confessed that he was the sole survivor of the three forgers.

Fine examples of pottery and porcelain have always commanded high prices, which have, in turn, encouraged the making of forgeries and reproductions. Since many European factories tried to imitate Italian majolica during the 19th century when it was especially popular, forgeries are common. The work of Urbino, Castel Durante, Faenza, and Gubbio was copied freely, and, to a lesser extent, so were the wares of Orvieto and Florence. Most of these forgeries are not close enough to deceive a reasonably expert eye. Potters used natural deposits the impurities of which, for good or ill, often affected the final result; until recently it has been impossible to procure materials in a pure state. In all but a few isolated instances (some German stoneware reproductions, for example) the forger no longer has access to these original deposits and he has to imitate the effect of the impurities as best he can. Although the best forgeries are often remarkably close to the originals, they are not very numerous.

In the composite fraud, or pastiche, the forger combines copies of various parts of another artist’s work to form a new composition and adds a few connecting elements of his own to make it a convincing presentation. This type of forgery is more difficult to detect than the copy. Such a combining of various elements from different pieces can be very deceptive, because a creative artist often borrows from his own work. In fact, the similarity of a figure or an object in a forgery to that in a well-known work of art often adds to the believability of the new creation.

The Dutch forger Han van Meegeren employed a combined composite and stylistic procedure when he created seven paintings between 1936 and 1942 based on the work of Johannes Vermeer. In The Supper at Emmaus he combined figures, heads, hands, plates, and a wine jar from various early genuine Vermeers; it was hailed as a masterpiece and the earliest known Vermeer. Ironically, van Meegeren never was detected as a forger. At the end of World War II he was arrested for having sold a painting attributed to Vermeer to one of the enemy and was accused of being a collaborator. He chose to reveal himself as a forger, which was a lesser offense, and proved his confession by painting another “Vermeer” under the eye of the authorities.

A notable forger of the late 20th century was Shaun Greenhalgh, who created several works of art in a variety of styles and, after carefully constructing a credible provenance for each, sold them over the course of roughly two decades with the help of his parents, George and Olive Greenhalgh. One of his notable forgeries was a stoneware sculpture, The Faun, thought to be a rare unglazed ceramic sculpture by Paul Gauguin, another was the Amarna Princess believed to date from 1350 BC.

A variation in composite forgery, quite common with inlaid French furniture, involves the use of parts from damaged but genuine pieces to create a single complete piece that may or may not resemble one of the pieces from which it has been made. These made-up pieces are still considered forgeries. In composites of archaeological material only one part may be ancient, the balance being made up to complete the object. The head of a small terra-cotta figure may be ancient, the body and limbs of modern workmanship. A single ancient element in a composite forgery will help to deceive the buyer.

Most difficult of all to detect is the forgery done in the style of a particular artist or age. If the forger is skillful and is able to absorb the attitudes, conventions, and techniques of the period, he can often create a very successful piece of duplicity.

The work of the Italian Alceo Dossena belongs in this class. He very competently forged works that were acquired by collectors and museums throughout the world. From 1916 to 1928 he produced hundreds of forgeries created as original expressions of archaic Greek, medieval, and Renaissance sculptors.

A newly discovered type of art inevitably brings on a flood of forgeries. At the end of the 19th century, when the first small, attractive Tanagra figurines were found in Greece, the market very shortly was flooded with a myriad of fraudulent Tanagra terra-cotta statuettes. In the mid-20th century, African primitive art became very popular, and woodcarvers from Italy to Scandinavia responded to supply the demand. Later, a very early civilization was discovered in Turkey, and the few genuine Anatolian ceramic pieces that appeared on the market were followed immediately by very competent forgeries apparently made in the same location as the ancient pieces. The lack of knowledge about genuine pieces made detection extremely difficult.

Detection of forgeries in the visual arts

The key to detecting forgery of unique objects lies in the fact that every object has within itself evidence of the time and the place in which it was made. The two main approaches, stylistic and technical analysis, are complementary and are best used together.

Stylistic analysis is subjective: it rests on the astute eye of the art historian. Each artist has a style, a flair, a verve unique to himself, and this can be recognized. His style will undergo change throughout his career, and this, too, can be stylistically analyzed and documented from his known works. When an unknown work purporting to be by a certain artist is discovered, the art historian attempts to fit it into the overall body of works by this artist. The subject matter, the brushwork, the choice of colours, and the type of composition are all consistent elements in a given artist’s production. Any variation immediately arouses suspicion. When the idiosyncrasies of an artist’s brushwork are studied, a fraud can sometimes be detected in much the same way a handwriting forgery is proven. In ancient works, particularly in antiquities, the scholar must examine the iconography of a piece. Forgers rarely have the scholarly background to combine iconographic elements correctly, and their errors often betray them.

An object must also be studied for its purpose. Ancient works were made for functional purposes. A forger usually makes an attractive piece often inconsistent with that purpose. As they were used most ancient pieces developed signs of wear. These rubbed and worn areas should appear in logical places on the object.

Documentation is also an important area of investigation. The apparent authenticity of many spurious pieces is bolstered by false documents to attest to the point of origin, former owners, and expert opinions concerning the pieces. A careful examination of these records often detects the forgery.

The hardest deception to detect is usually one that has been made recently. The forgery is a product of the time in which it was made, and the forger is closer to current understanding of the artist or period forged. The forgery, therefore, is often more appealing than a genuine work of art. As a forgery ages, viewpoints and tastes shift, and there is a new basis of understanding. Consequently, a forgery rarely survives more than a generation.

Technical analysis, an objective approach, rests on an arsenal of equipment and tests. The fundamental principle is the comparison of a suspected work with a genuine work of the same artist or period. The suspected piece must show the same pigments or materials used and comparable age deterioration. Inconsistencies automatically cause the piece to be suspect. Oil paintings dry out and develop a crackle, bronzes oxidize, and ancient glass buried in the ground develops iridescent layers. The microscope is the most useful basic tool: a close examination of the physical condition often will show if the aging is genuine or has been artificially induced. The type of tools used by the artist can be detected from an examination of their telltale traces.

Ultraviolet rays readily reveal additions or alterations to a painting, since the varnish layers and some of the paint layers fluoresce to different colours. Ultraviolet is also used in the examination of marble sculpture. Old marble develops a surface that will fluoresce to a yellow-greenish colour, whereas a modern piece or an old surface recently recut will fluoresce to a bright violet. Infrared rays can penetrate thin paint layers in an oil painting to reveal underpainting that may disclose an earlier painting on the same canvas, or perhaps a signature that has been painted out and covered by a more profitable one. X rays are used to examine the internal structure of an object. A carved wooden Virgin supposedly of the 15th century but revealing modern machine-made nails deep inside is obviously a fraud. A forger usually works for the surface effect and is not concerned with the internal structures.

Sometimes it is necessary to remove small bits of materials from a work and subject them to various analyses. Chemical analysis is particularly valuable in determining the pigment used because many of the paints available to the modern forger were unknown in earlier times. Today titanium, a 20th-century product, is used to make the white pigment in most oil paints, whereas white lead was the element used in the time of Rembrandt. Many ancient colours were manufactured by grinding natural minerals such as lapis lazuli for blue and malachite for green. Today cheaper synthetic chemicals are used. Some chemical tests, however, require the removal of more ancient material than is desirable. In that event a speck as small as the head of a pin can be analyzed spectrographically. From the burning of a minute sample a photographic record of the spectrum of the light emitted is analyzed to reveal the elements present and their relative percentages.

The dating of an object by the study of radioactive decay of carbon-14 has had little application in the detection of art forgery because of the large quantities of material that must be destroyed. Thermoluminescent dating is based on the slight damage to all matter, including clays, by the faint nuclear radiation present in the earth. Magnetic dating of ceramic objects is based on the slow but perceptible shift of the earth’s magnetic field over the centuries.

Considerations of aesthetics and risk

One may logically question the real meaning of the difference between a genuine and a spurious work of art when in many cases it requires such expert study to detect the difference between the two. Or to phrase it another way, what is the difference in value of a work of art that has been on view in a museum for 40 years, after it has been proved to be false? This is a somewhat philosophical point in that the object itself has not changed, only our opinion of it. Its monetary value has been reduced from that of a rare, expensive, original piece to that of an attractive but spurious imitation. Its aesthetic quality has become a real danger, as it is a perversion of the truth. The forgery presents a false understanding of the work of an artist or an ancient culture, one which has been perverted in its modern translation. To appreciate the work of ancient artists their work must be studied alone and not be diverted by forgeries, or one will be inexorably misguided.

Despite all the studies and technical tests available, forgeries will still be made. The 20th-century art forger is far better equipped and much more knowledgeable than his predecessor. The demand for rare works of art has increased, and he will attempt to supply them. In collecting, whether by the private collector or by a museum, there comes a point when, after all the studies and all the tests are conducted, a decision has to be made as to whether or not to purchase a piece in question. The element of risk can be minimized but not eliminated. At this point, the collector should be ready to back his opinion with the purchase price. In order to acquire great pieces, particularly from newly discovered and relatively unknown cultures, it is necessary to take a calculated chance. The collector who has never bought a forgery probably has never bought a great piece of art.